Facebook Notifications

Hey guys I have my Facebook notifications set to display in notification center and to play the sound. I have to main problems.
1.) it seems like I am not receiving all my notifications. Shouldn't I receive everything that appears as a notification in Facebook on my iPhone?
2.) no matter what settings I change or toggle I never hear the sound (yes it is not on silent) I will get the notification sporadically in notification center but never a sound.